Question: $ { \left[\begin{array}{r}{3} \\ {-1} \\ {1}\end{array}\right]+\left[\begin{array}{r}{-1} \\ {2} \\ {1}\end{array}\right] = {?} } $
To find the sum of two matrices, add the corresponding items between each matrix. ${\left[\begin{array}{r}{3}+{-1} \\ {-1}+{2} \\ {1}+{1}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{r}{2} \\ {1} \\ {2}\end{array}\right]}$